In prior-art air bag gas generators, the filter ring is surrounded by a filter chamber housing. The filter chamber housing is provided with punched-out or drilled discharge openings or discharge openings arranged in any other way. Through these openings the propellant gas flows into the air bag (cf., e.g., West German Offenlegungsschrift No. DE-OS 25,38,386, corresponding to U.S. Pat. No. 4,278,638 of Jul. 14, 1981, West German Offenlegungsschrift No. DE-OS 29,15,202, West German Offenlegungsschrift No. DE-OS 37,42,383, and EP 0,012.627 B1).
In the gas generator according to U.S. Pat. No. 4,278,638 (West German Offenlegungsschrift No. DE- OS 29,15,202), the gas generator is made of sheet metal and is provided with a toroidal combustion chamber, which surrounds a central pipe with an igniting unit. To achieve this, the combustion chamber housing is composed of the inner section of an annular housing shell, with S-shaped cross section, and a cover. The inner edge of the housing shell is connected to the central pipe, and the inner edge of the cover is also connected to the central pipe, and its outer edge is connected to the housing shell. A cover plate is provided with an outer circumference designed as a flange for fastening the generator on the vehicle. This cover plate delimits, together with the outer section of the housing shell, the filter chamber to the outside. Discharge openings, through which the propellant gas flows into the air bag, are punched in the outer section of the housing shell.
The high noise level during the burning off of the propellant is especially disadvantageous in the prior-art gas generators. In addition, it is desirable to reduce the manufacturing costs, the intrinsic weight of the gas generator, and the load of the filter ring, with increased effectiveness of the filter ring.